Santa Cruz frames are the most desirable out there. Most of the frame options are now carbon, but there are still a few alloy models in the range.
Frames from Santa Cruz include the 5010 their 130mm trail bike, the 150mm travel trail/enduro Bronson and the aggressive 170mm Nomad enduro model. The alloy Heckler is a 150mm trail bike which is excellent value.
If you're after bigger wheels you have the choice of the 110mm 29er Tallboy trail bike or the 150mm Hightower which is a hugely capable bike for trail and enduro adventures.
Santa Cruz hardtail frames include XC focussed Highball 29er, the trail ready Chameleon and the dirt/slalom Jackal.
Santa Cruz make one DH model, the genre topping V10 downhill bike.